In heat exchangers of the above-mentioned type the input and extract air usually pass in opposite directions on each side of heat-exchanger sections shaped with rhomboid cross section in a drum, as described in U.S. Pat. No. 4,377,201, for instance. The oppositely-directed air flows are thus forced to run in meandering flow, thereby entailing relatively high power consumption.
To reduce the power consumption a heat exchanger is known through EP-A-0 462 199 in which the heat-exchanger sections are arranged with spaces aligned with each other so that one of the air flows (normally the input air) has a linear direction of flow. However, the linear flow is disturbed by the formation of eddy currents each time it enters or leaves the heat-exchanger sections. These eddy currents thus still cause increased power consumption, i.e. poorer efficiency.
In known heat exchangers of the above-mentioned types, each heat-exchanger section is surrounded by a frame. This means that the degree of heat recovery is deteriorated since a considerable part of the available heat-exchanger surface is taken up by the frame.
The principle on which the present invention is based is shown in DE,A1,3137296. However, this publication does not show the specific features of the present invention which give the heat exchanger according to the invention properties not previously achieved.